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Jessi: Shhhh. Cover your eyes for a moment and just listen. What you hear? I hear my chemistry set bubbling... and Squeaks, is that you?

Sounds are all around us, all the time. There are so many of them, and we call sounds by a lot of different names. Like if a sound is really loud and kind of unpleasant, like when there's a lot of traffic going by sometimes call it noise. And if a sound is made by an instrument like a piano or a ukulele, we call it a note. And we call lots of notes together music. And some words are kind of like the sounds themselves like when fireworks go boom, popcorn pops and bells go ding-a-ling.

It doesn't matter what makes a sound though, all sounds are made the same way: through vibrations. When something vibrates, it moves back and forth really fast. So fast in fact that our eyes often can't see it moving. But other parts of our body can sense vibrations and about you know what parts those are. That's right our ears! So how does sound get from say, a bell, to our ears?

The air all around us is native title particles and these particles are what carry sound. We can use marbles to demonstrate the teeny tiny particles that make up the air. Let's see how! If we put a few marbles together so they're touching and then roll another marble so that crashes into them, the group of marbles will move. That's kinda what happens with sound. When we ring a bell, we cause the metal that makes up the belt on vibrate really fast back and forth, and the vibration of the bell also shakes up the particles that make up the air around it and makes them vibrate, then those particles run into the air particles next to them and so on.

You can also think about it like dominoes, with the vibration getting passed along from one bunch of particles in the air to the next. We call this path of vibration a wave. Now how do we hear those vibrations? If we could look deep inside our ears, we'd see a special little part that kind of looks like the top of a drum. When sound waves make it all the way to end into our ears, they make this part of our ear vibrate. The vibrations keep going moving even deeper into our ear, until they finally get to the spot that sends a message to our brain.  And that message says "hey! We're hearing something!"

Now, who's ready to make some vibrations? We can make a kind of musical instrument that will help us to see the vibrations that we make. All we need is an empty can, like a coffee can, and a rubber band that's just big enough to stretch around the can stop to it's bottom. Stretch the rubber band over the top of the coffee can and ta-da! We have an instrument. One that's kind of like a guitar.

Let's put the rubber band gently. Does it make a sound? It sure does. And if we look very very closely, we can see that the rubber band is moving back and forth. When we put on the rubber band and let it go, we're causing it to vibrate. These vibrations travel into the air, making the air particles move through the air to our ears in a sound wave.

If we pull kind of gently, the sound is kind of soft. But if we pull the harder, the sound gets louder. And if we grab the rubber band while it's moving and stop it from vibrating... we also stop the sound. Hey, we made some pretty good vibrations!

So whenever you hear sound, you know that something somewhere is vibrating, and those vibrations are traveling through the air and into your ears. So thanks to all of you who asked us how sound works, and make sure to check back every week to learn more science with Squeaks and me, and we'll see you next time.

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